Steroid bisphosphonates

ABSTRACT

Bisphosphonate derivatives of hydroxy steroids which are bone resorption inhibitors or bone formation stimulators, the derivatives having at least one group A in place of a hydroxy group on the steroid molelcule, where A is a group of forumla (A) where X is: (i) St--O--CO-- where St is the residue of the hydroxy steroid given by removal of an OH group; or (ii) R 1  --O--CO-- where R 1  is an alkyl, alkenyl, cycloalkyl, aralkyl or aryl group, any of which may optionally be substituted, and the salts and solvates of these compounds. The steroid is typically 17β-oestradiol, oestrone, testosterone, norethindrone, androsterone, norethandrolone or nandrolone. The derivatives can be used in the treatment of bone disorders such as osteoporosis. ##STR1##

This application is a 371 of PCT/GB97/01748 filed Jun. 26, 1997.

This invention concerns steroid derivatives and in particularbisphosphonate derivatives of hydroxy steroids for use in the preventionor treatment of osteoporosis and related bone disorders.

Hydroxy steroids such as oestradiol and testosterone have been proposedfor use in the treatment of osteoporosis, either by inhibition of boneresorption or stimulation of bone formation, and bisphosphonates such asdisodium etidronate and clodronate are also known as bone resorptioninhibitors. Certain bisphosphonate derivatives of steroids have alsorecently been proposed for these purposes in EP-A-0496520 andEP-A-0548884. In the compounds of EP-A-0496520 the steroidal group islinked to the bisphosphonate group by a carbamate or carbonate group,and EP-A-0548884 describes steroid bisphosphate ethers.

We have now found a new group of bisphosphonate derivatives of suchsteroids which are linked by a carboxyl group and, by virtue of theaffinity of the bisphosphonate groups for bone, have the potential totarget the active steroid selectively on bone and then release theactive material in situ by hydrolysis. The compounds of the inventionare thus of interest in the prevention or treatment of osteoporosis andother bone disorders such as Paget's disease, bone metastases andmalignant hypercalcaemia.

The compounds of the invention are derivatives of hydroxy steroids whichare themselves bone resorption inhibitors or bone formation stimulatorsand thus useful in the prevention or treatment of osteoporosis, thederivatives having at least one group A in place of a hydroxy group onthe steroid molecule, where A is a group of the formula ##STR2## where Xis: (i) St--O--CO-- where St is the residue of the hydroxy steroid givenby removal of an OH group,

(ii) R¹ --O--CO-- where R¹ is an alkyl, alkenyl, cycloalkyl, aralkyl oraryl group, any of which may optionally be substituted, or

(iii) a hydrogen atom. The invention also includes salts and solvates ofthese compounds.

The compounds of the invention may thus have the formula St-A where Stand A are as defined above. Particular groups of compounds of interestare those of the formulae:

    (St--O--CO).sub.2 CHCH.sub.2 CH(PO(OH).sub.2).sub.2        (1)

    (St--O--CO)(R.sup.1 --O--CO)CHCH.sub.2 CH(PO(OH).sub.2).sub.2(2)

    (St--O--CO)CH.sub.2 CH.sub.2 CH(PO(OH).sub.2).sub.2        (3)

Where the steroid contains more than one hydroxy group, only one isusually replaced by a group A, but the invention includes derivatives ofsuch compounds in which two or more hydroxy groups are replaced by Agroups.

The structural variety of the compounds of the invention allows theirhydrolysis properties to be modulated as required. For example, mostknown steroid-bisphosphonate conjugates, particularlyoestradiol-biphosphonates, hydrolyse very rapidly whereas slowerhydrolysis and hence slower release of the steroid is often desirable.Compounds of formula (1) above such as the compound (4) below whichcontains two steroid units are resistant to hydrolysis and thusadvantageous when a slower rate of steroid release is required. On theother hand, compounds containing only one steroid unit are lessresistant to hydrolysis and thus more suitable when rapid steroidrelease is required. The compounds of formula (1) also enable twodifferent steroid units to be included in the same molecule, and thisallows steroids of different activities to be delivered at the sametime.

The parent hydroxy steroid may be an oestrogen, androgen, anabolicsteroid, glucocorticoid or progestagen which inhibits bone resorption orstimulates bone formation, such as for example 17β-oestradiol, oestrone,testosterone, norethindrone, androsterone, norethandrolone andnandrolone. These compounds generally have a hydroxy group at the 3- or17- position or both, and further examples of hydroxy steroids which maybe used are listed in EP-A 0496520.

In the group X, R¹ may be a C₁₋₆ alkyl (e.g. methyl, ethyl, isopropyl ort-butyl), C₂₋₆ alkenyl (e.g. allyl), C₃₋₈ cycloalkyl (e.g. cyclopentylor cyclohexyl), phenyl (C₁₋₆)alkyl or a mono- or bicyclic aryl group(e.g. phenyl or naphthyl). The alkyl and alkenyl groups may for examplebe substituted by one or more halogen atoms (e.g. chlorine) and thecycloalkyl groups by one or more C₁₋₄ alkyl groups or halogen atoms(e.g. chlorine). The aryl groups may be substituted by one or morehydroxy groups, as in naphthol.

The compounds of the invention are capable of forming salts with basesand examples of such salts are alkali metal (e.g. sodium) and alkalineearth metal (e.g. calcium) salts. Some compounds of the invention existin enantiomeric forms and all such forms are included.

Particular compounds of importance have the following formulae: ##STR3##The compounds of the invention are useful in the prevention or treatmentof osteoporosis and the other bone disorders referred to above in manand animals and they may be formulated for these purposes aspharmaceutical compositions together with one or more pharmaceuticallyacceptable carriers, excipients or diluents. The active ingredient inthese compositions may for example be a compound (4), (5) or (6) shownabove.

The pharmaceutical compositions of the invention may be in a formsuitable for oral, buccal, parenteral or topical administration.

For oral administration, compositions may be in the form of, forexample, tablets, lozenges or capsules containing pharmaceuticallyacceptable excipients such as binding agents, fillers, lubricants,disintegrants or wetting agents. The tablets may also be coated by knownmethods. Liquid preparations for oral administration may be in the formof solutions, syrups or suspensions and may contain pharmaceuticallyacceptable additives such as suspending agents, emulsifying agents,non-aqueous vehicles and preservatives.

The compositions may also be formulated for use by injection and may bepresented in unit dose form, e.g. in ampoules. The compositions forinjection may be in the form of suspensions, solutions or emulsions, inoily or aqueous vehicles, and may contain formulatory agents such assuspending, stabilising, solubilising and/or dispersing agents.

The compositions may also be in a form suitable for topicaladministration, e.g. transdermal patches, ointments, creams and lotions.

The compounds of the invention may be administered in combination withother pharmaceutically active ingredients.

The total daily dosages of compounds of the invention employed inmedicine will suitably be in the range 0.001-10.0 mg/kg bodyweight andthese may be given in divided doses, i.e. 1-4 times per day.

Compounds of the invention in which X is a group (i), for examplecompounds of formula (1) above, may be prepared by transesterificationof the carboxylic ester group of a compound of formula (7) ##STR4##(where R² and R³ are C₁₋₆ alkyl groups, e.g. ethyl, and may be the sameor different) with the hydroxy steroid (StOH), to give a phosphonateester (8) of the formula (St--O--CO)₂ CHCH₂ CH(PO(OR₃)₂)₂, followed byhydrolysis of the phosphonate ester group to give the desiredbisphosphonic acid.

The transesterification of (7) may be effected in the presence of a basecatalyst such as DMAP (dimethylaminopyridine), for example in ahydrocarbon solvent at any suitable temperature up to reflux.

When the parent hydroxy steroid contains a further hydroxy group whichis to remain in the final product, this should be protested during thetransesterification reaction (for example as a benzyl ether) and theprotecting group subsequently removed.

The hydrolysis of the ester (8) may be carried out with a tri (C₁₋₆alkyl) silyl halide such as trimethylsilyl bromide, for example in ahalogenated hydrocarbon solvent.

The bisphosphonates (7) may be prepared by first reacting a methylenebisphosphonate (9) ##STR5## with paraformaldehyde (e.g. in the presenceof a base catalyst such as diethylamine) followed by elimination ofmethanol to give a methylidene compound (10) ##STR6## which is thenreacted with a dialkylmalonate (in which the alkyl group is R² asdefined above) in the presence of a base catalyst (e.g. sodiumethoxide).

Compounds in which X is a group (iii), for example compounds of formula(3) above may be prepared by esterification of the hydroxy steroid(StOH) with the acid (11) ##STR7## The reaction may be carried out inthe presence of a base and an activating agent such as EDCI(N-(3-ethyldimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride). Thephosphonate ester groups may then be removed by hydrolysis as describedabove to give the required bisphosphonic acid.

Again, when the hydroxy steroid contains a further hydroxy group whichis to be retained, it should be protected during the reaction andsubsequently removed.

The acids (11) can be prepared from a methylidene compound (10) above byaddition of a dibenzyl malonate, in the presence of a non-nucleophilicbase catalyst, to give the ester (12) ##STR8## followed byhydrogenolysis (e.g. over palladium on carbon) and subsequentdecarboxylation (e.g. by heating).

Compounds in which X is a group (ii), for example compounds of formula(2) above may be prepared from a malonate (13) of the hydroxy steroid

    R.sup.1 OCO.CH.sub.2.CO.OSt                                (13)

by reaction with a methylidene compound (10) in the presence of anon-nucleophilic base to give the addition product (14) ##STR9##followed by removal of the phosphonate ester group by hydrolysis asdescribed above to give the desired bisphosphonic acid.

THE FOLLOWING EXAMPLES ILLUSTRATE THE INVENTION. EXAMPLE 1 Synthesis ofTetraethyl ethylidene bisphosphonate (16) ##STR10## Tetraethyl methylenebisphosphonate (47.4 g, 0.165 mol, 1.0 equiv.), paraformaldehyde (24.75g, 0.825 mol, 5.0 equiv.), diethylamine (17.1 ml, 12.1 g, 0.165 mol, 1.0equiv.) were added to methanol (470 ml). The reaction mixture was heatedat 60 ° C. until the mixture became a colourless solution (30 minutes),and stirred for a further 15 hours at room temperature. The mixture wasconcentrated under reduced pressure, and toluene (150 ml) added. Thesolvent was removed under reduced pressure. The addition of toluenefollowed by a second concentrating process aided the removal of methanolfrom the crude viscous intermediate product 15. δ_(H) (CDCl₃) 1.29 (12H,t, J=8, P--OCH₂ CH₃), 2.67 (1H, tt, J_(H-P) =24, J_(H-H) =5, P₂ CHCH₂OCH₃), 3.32 (3H, s, --OCH₃), 3.86 (2H, td, J_(H-P) =17, J_(H-H) =5, P₂CHCH₂ OCH₃), and 4.15 (8H, m, P--OCH₂ CH₃). ##STR11## Toluene-p-sulfonicacid (0.15 g, catalytic) was added to a solution of crude tetraethyl(2-methoxy) ethylidene bisphosphonate 15 in toluene (250 ml). Thereaction mixture was heated overnight, under reflux conditions, afterthis period of time elimination had gone to completion. The reactionmixture was washed with water (3×100 ml), and the solvent removed underreduced pressure to yield 16 as an oil (43.16 g, 88% for 2 steps);ν_(max) 3020, 2960, 1485, 1452, 1402, 1270 (b), and 1050 (b); δ_(H)(CDCl₃) 1.30 (12H, t, J=8.0, P--OCH₂ CH₃), 4.0-4.2 (8H, m, P--OCH₂ CH₃),and 6.94 (2H, dd, trans J_(P-H) =40.0, cis J_(P-H) =36.4, P₂ C=CH₂);δ_(C) (CDCl₃) 16.15 (4C, t, J=3.4, P--OCH₂ CH₃), 63.08 (4C, d, J=3.4,P--OCH₂ CH₃), 132.58 (1C, t, J=127, P--C--P) and 149.11(1C, s, --P₂C═CH₂); m.s. (CI) m/z 301 (M⁺ +H). EXAMPLE 2 Synthesis of Hexaethyl-[3,3-bis(oxycarbonyl)]propylidene bis[phosphonate] (17) ##STR12##Sodium (0.23 g, 10 mmol, 0.1 equiv.) was dissolved in ethanol (100 ml)and stirred at 0° C. under a nitrogen atmosphere. The mixture wasallowed to warm to ambient temperature until all the sodium haddissolved. The sodium ethoxide solution prepared in situ was transferedvia a cannula to a solution of 16 (30.0 g, 100 mmol, 1.0 equiv.) anddiethyl malonate (15.20 ml, 16.02 g, 100 mmol, 1.0 equiv.) in ethanol(50 ml). The reaction mixture was stirred under an atmosphere ofnitrogen at ambient temperature for 30 minutes. The reaction mixture waswashed with aqueous HCl 1M (3×100 ml) and extracted into CH₂ Cl₂ (200ml). The organic fraction was collected and dried with anh. MgSO₄, thesolvent was removed under reduced pressure final traces of solvent wereremoved under high vacuum. The desired product 17 was isolated as an oilin excellent yield (43.8 g/95.1%). (Found: C 43.97 H 7.55, C₁₇ H₃₄ O₁₀P₂ requires: C 44.35 H 7.44); ν_(max) 3010, 1749, 1732, 1270 (b), and1045 (b) cm⁻¹ ; δ_(H) (CDCl₃) 1.28 (6H, t, J=7.16, CO₂ CH₂ CH₃), 1.35(12H, t, J=7.12, PO₂ CH₂ CH₃), 2.33-2.75 (3H, m), 3.97 (1H, t, J=7.68,--CH(CO₂ Et)₂), and 4.12-4.27 (12H, m); δ_(C) (CDCl₃) 14.48 (2C, s,--CO₂ CH₂ CH₃), 16.71 (4C, d, J_(CP) =PO₂ CH₂ CH₃), 25.29 (1C, t, J_(CP)=5, --CHCH₂ CH--), 34.71 (1C, t, JCP=132, P--C--P), 50.51 (1C, t, J_(CP)=8, --CH₂ CH(CO₂ Et)₂, 61.97 (2C, s, --CO₂ CH₂ CH₃), 63.22 (4C, t,J_(CP) =, PO₂ CH₂ CH₃), and 169.31 (2C, s, --CO₂ Et); δ_(P) CDCl₃)22.33;m/z (CI) 461 (M⁺ +H). EXAMPLE 3 Synthesis of Tetraethyl{3,3-bis-[3-benzyloxy-estra-1,3,5-triene-17β-yloxycarbonyl]propylidene}bis[phosphonate](18) ##STR13## 4-(N,N-dimethylamino)pyridine (0.013 g, 0.11 mmol, 0.1equiv.) and 3-benzyl-17β-oestradiol (0.861 9, 2.39 mmol, 2.2 equiv.)were added to a solution of 17 (0.50 g, 1.09 mmol, 1.0 equiv.) intoluene (10 ml). The reaction mixture was heated under reflux for 11days under an atmosphere of nitrogen. The solvent was removed underreduced pressure and the crude product absorbed onto silica gel. Theproduct was purified by silica gel flash column chromatography, theeluent used was 1-3% methanol in CH₂ Cl₁ the desired product wasobtained as a viscous oil (0.80 g, 67%); ν_(max) 3017, 2936, 1724, 1605,1498, 1203 (b), and 929; δ_(H) (CDCl₃) 0.84 (3H, s, 18'--CH₃), 0.88 (3H,s, 18'--CH₃), 1.23-1.97 (21H, m), 1.35 (12H, t, J=7), 2.15-2.36 (13H,m), 4.72-4.81 (2H, m, 17'H), 5.05 (4H, s, --OCH₂ Ph), 6.74 (2H, s, 4'H),6.80 (d, 2H, J=9, 2'H), 7.23 (d, 2H, J=9, 1'H), and 7.30-7.47 (m, 10H);δ_(C) (CDCl₃) 13.09, 13.20, 17.43, 17.51, 24.35, 26.19, 27.24, 28.29,28.53, 30.82, 35.51 (t, J_(CP) =132, PCP), 37.95, 44.15, 44.31, 44.84,50.80, 51.38 (t, J_(CP) =7.3, --CHCH₂ CH(CO₂ R)₂), 63.83 (t, J_(CP)=6.9, --CH₂ CH(CO₂ R)₂), 71.00, 85.02 (d, J_(CP) =10.4, PO₂ CH₂ CH₃),113.39, 115.92, 127.42, 128.49, 128.89, 129.59, 133.73, 138.39, 138.95,157.84, and 169.96 (d, J_(CP) =3.5, --CH(CO₂ R)₂); δ_(P) (CDCl₃) 20.4;m/z (+ve ion FAB) 1094 (M⁺ +H, 100). EXAMPLE 4 Synthesis of Tetraethyl{3,3-bis[estra-1,3,5-triene-3-hydroxy-17β-yloxycarbonyl]propylidene}bis[phosphonate] ##STR14## To a solution containing 18 (692 mg, 0.633mmol, 1.0 equiv.) in teahydrofuran/methanol 1:1 (10 ml) was added 10%Pd/C (140 mg). The reaction mixture was shaken under an atmosphere ofhydrogen (1 bar) for 6 hours. The reaction mixture was filtered, takenup into CH₂ Cl₂ and washed with brine. The organic layer was collectedand dried with anh. MgSO₄ and the solvent removed under reducedpressure. The product was purified further by silica gel flash columnchromatography, eluted with 3-5% methanol in CH₂ Cl₂. The solvent wasonce again removed and the product was produced as a foam under highvacuum (557 mg, 96.4%); (Found: C, 64.68; H, 7.76. C₄₉ H₇₀ O₁₂ P₂requires: C, 64.46; H, 7.73); δ_(H) (CDCl₃) 0.775 (3H, s, 18'--CH₃),0.781 (3H, s, 18'--CH₃), 1.15-1.87 (21H, m), 1.34 (12H, t, J=6.8,P--OCH₂ CH₃), 2.09-2.33 (6H, m), 2.49 (2H,heptet, J=7.6, P₂ CHCH₂ CH(CO₂R)₂), 2.66 (1H, tt, J_(P-H) =24, J_(H-H) =7.2 P₂ CHCH₂ CH(CO₂ R)₂), 2.81(4H, m), 4.05 (1H, t, J=7.6, P₂ CHCH₂ CH(CO₂ R)₂), 4.16-4.24 (8H, m,P--OCH₂ CH₃) 4.71 (2H, q, 9.2, 17'H), 6.58 (2H, s, 4'H), 6.66 (2H, d,J=8, 2'H), and 7.08 (2H, d, J=8.8, 1'H); δ_(C) (CDCl₃) 11.93 (1C, 18'C),12.03 (1C, 18'C), 16.29 (4C, d, J=5, P--OCH₂ CH₃), 23.22 (2C), 24.95(1C, b--P₂ CHCH₂ CH--), 26.16 (2C), 27.18 (1C), 27.37 (1C), 29.53 (2C),34.17 (1C, t, J=134, P--C--P), 36.81 (2C), 38.56 (2C), 42.98 (2C), 43.17(1C), 43.68 (1C), 49.64 (2C) 50.23 (1C, t, J=9, P₂ CHCH₂ CH(CO₂ R)₂)63.06 (4C, t, J=7, P--OCH₂ CH₃), 83.95 (1C, 17'C), 84.09 (1C, 17'C),112.77 (2C), 115.31 (2C), 126.22 (2C), 131.48 (2C), 131.53 (2C), 137.79(2C), 154.23 (2C), and 168.84 (2C, --CO₂ R); δ_(P) (CDCl₃) 20.7(s); m/z(+ve ion FAB) 913 (M⁺ +H, 76), 159 (100) . EXAMPLE 5 Synthesis of3,3-Bis-(estra-1,3,5-trien-3-hydroxy-17β-yloxycarbonyl) propylidenebis(phosphonic acid) (20) ##STR15## To a solution of 19 (250 mg, 0.275mmol, 1.0 equiv. ) in CCl₄ /CHCl₃ 1:1 (3 ml) was added trimethylsilylbromide (1.24 ml, 1.47 g, 9.62 mmol, 35 equiv.) and the mixture stirredfor 24 hours under a nitrogen atmosphere. Water (5 ml) was added and anoff white solid formed. The precipitate was filtered and washed withcold water and CH₂ Cl₂. The product was dried under high vacuum andobtained as an off white powder (206 mg, 94%) which decomposes at 180°C.; δ_(H) (CD₃ OD) 0.85 (3H, S, 181'--CH₃), 0.86 (3H, S, 18'--CH₃), 1.202.05 (21H, m), 2.10-2.30 (5H, m), 2.38-2.50 (3H, m), 2.70 2.81 (4H, m),4.08 (1H, t, J=7, --CH₂ CH(CO₂ H)₂), 4.72 (2H, t, J=8, 17'H), 6.47 (2H,d, J=2, 4'H), 6.53 (2H, dd, J=9, J=2, 2'H), and 7.05 (2H, d, J=9, 1 'H);δC (CD₃ OD) 12.64 (1C, 18'C), 12.71 (1C, 18'C), 24.22 (2C), 26.37 (1C,b, --P₂ CHCH₂ CH--), 27.44 (2C), 28.45 (2C) 28.52 (2C), 30.63 (2C),36.79 (1C, t, J=127, P--C--P), 38.16 (2C,b), 40.18 (2C), 44.28 (1C,13'C), 44.40 (1C, 13'C), 45.10 (2C), 50.94 (2C), 52.04 (1C, b, --CH(CO₂R)₂), 85.26 (1C, 17'C) 85.34 (1C, 17'C), 113.79 (2C), 116.08 (2C),127.21 (2C) 132.36 (2C), 138.73 (2C), 155.94 (2C, 3'C), and 170.49 (2C,--CO₂ R); δ_(p) (CD₃ OD) 22.6; m/z (--ve ion FAB) 799 (M⁻ --H, 100).EXAMPLE 6 Synthesis of Tetraethyl [3,3bis(benzyloxycarbonyl)]propylidene bis [phosphonate] (21) ##STR16##Tetraethyl ethylidene bisphosphonate 16 (1.00 g, 3.33 mmol, 1.0 equiv.),and dibenzyl malonate (0.83 ml, 0.946 g, 3.33 mmol, 1.0 equiv.) weredissolved in tetrahydrofuran (15 ml). Lithium bis(trimethylsilyl) amidesolution in tetrahydrofuran (1M), (0.33 ml, 0.33 mmol, 0.1 equiv.), wasadded to the reaction mixture and stirred for one hour at roomtemperature. Saturated aqueous ammonium chloride (50 ml) was added tothe reaction mixture and the product extracted into CH₂ Cl₂ (100 ml).The organic layer was collected and dried with anh. MgSO₄, the solventwas removed under reduced pressure. The crude product was absorbed ontosilica gel and purified by silica gel flash column chromatography,eluted with 2-3% methanol/CH₂ Cl₂. The product was isolated as acolourless oil (1.12 g, 58% yield); δ_(H) (CDCl₃) 1.30 (6H, t, J=7.1,--OCH₂ CH₃), 1.31 (6H, t, J=7.1, --OCH₂ CH₃), 2.37-2.74 (3H, m),4.07-4.24 (9H, m), 5.14 (4H, s, --OCH₂ Ph), and 7.24-7.35 (10H, m);δ_(C) (CDC₃) 16.10 (2C, --OCH₂ CH₃), 16.24 (2C, --OH₂ CH₃), 24.81 (1C,m, --CH₂ CHP₂) 34.11 (1C, t, JC-P =132.1, P--C--P), 49.93 (1C, t,J_(C-P) =7.8, --C(O)CHRC(O)), 62.66 (4C, m, --OCH₂ CH₃), 67.11 (2C,--OCH₂ Ph), 128.03 (4C, ortho C), 128.22 (2C, para C), 128.40 (4C, metaC), 135.12 (2C, 1' on Ph) and 168.41 (2C, --OC(O)CH); δ_(P) (CDCl₃)32.19; m/z (+ve ion FAB) (M⁺ +H) 585 (36), 369 (7), and 91 (100); HRMS(M⁺ +H) (Found: 585.20184 C₂₇ H₃₉ P₂ O₁₀ requires: 585.20185). EXAMPLE 7Synthesis of Tetraethyl 3,3bis(phosphono)-propylidene bis(carboxylicacid) (22) ##STR17## 21 (0.698 g, 1.19 mmol), was dissolved intetrahydrofuran (10 ml), and palladium activated charcoal (0.10g, cat.)added. The reaction mixture was stirred under an atmosphere of hydrogen,overnight, at room temperature. The reaction mixture was filtered andwashed with saturated aqueous ammonium chloride (50 ml). The product wasextracted into CH₂ Cl₂ and dried with anh. MgSO₄, the solvent wasremoved under reduced pressure, and the product dried under high vacuumas a white solid, (0.42 g, 88% yield); δ_(H) (MeOD) 1.35 (12H, t, J=6.6,--P--O--CH₂ CH₃), 1.74 (2H, heptet, J=7.7, P₂ CHCH₂ CH--), 2.08 (1H, tt,J_(P-H) =23.1, J=6.6, P--CHRP), 3.18 (1H, t, J=6.6, --CH₂ CH(CO₂ H)2),3.48-3.63 (8H, m, P--O--CH₂ CH₃); δC(MeOD) 16.55 (2C, P--O--CH₂ CH₃),16.68 (2C, P--O--CH₂ CH₂ CH₃), 25.95 (1C, t, J_(P-C) =4.0, P₂ CHCH₂CH--), 35.01 (1C, t, J_(P-C) =133.4, P--CHRP), 51.10 (1C, m, --CH(CO₂H)₂), 64.45 (4C, dd, J=9.4, 6.7, P--O--CH₂ CH₃), 171.84 (2C, --CO₂ H);δ_(P) (MeOD) 22.8; m/z (+ve icon FAB) (M⁺ +D) 406 (100), and (M⁺ +H) 405(90) EXAMPLE 8 Synthesis of Tetrathyl 4,4-bis(phosphono)-butanoic acid(23) ##STR18## 22 (0.200 g, 0.495 mmol), was heated to 130° C. for 3hours, under a steady stream of nitrogen. The product was obtained as acolourless oil (0.174 g, 99%); δ_(H) H(MeOD) 1.35 (12H, t, J=7.7, --OCH₂CH₃), 2.06-2.25 (2H, m, P₂ CHCH₂ CH₂ --), 2.6-2.69 (1H, m, --CDHCO₂ H),2.81 (1H, tt, J_(P-H) =24.2, J=6.6, --PCHP--), 4.11-4.25 (8H, m,P--O--CH₂ CH₃); δ_(C) (MeOD) 16.57 (2C, P--O--CH₂ CH₃), 16.71 (2C,P--O--CH₂ CH₃), 21.82-2.10 (1C, m, P₂ CHCH₂ CH₂ --), 32.53-33.07 (1C, mP₂ CHCH₂ CH₂ CO₂ H) 35.87 (1C, t, J=133.4, P--CHR--P), 64.07-64.36 (4C,m, --P--O--CH₂ CH₃), and 175.85 (1C, --CO₂ H); δ_(P) (MeOD) 24.9m/z (+veion FAB) 361 (100) (M⁻ -H, for di-deuterated product); HRMS (+ve ionFAB) (Found: 363.12997 C₁₂ H₂₅ D₂ O₈ P₂ requires: 363.13067). EXAMPLE 9Synthesis of Tetraethyl{3-[3-benzoyloxy)estra-1,3,5-trien-17β-yloxycarb-c-yl]propylidene}bis[phosphonate](24)##STR19##

23 (0.071 g, 0.20 mmol, 1.0 equiv.), 3-O-benzoyl-17β-oestradiol (0.089g, 0.24 mmol, 1.2 equiv.), and 4-(N,N-dimethylamino)pyridine (0.005 g,0.04 mmol, 0.2 equiv.), were dissolved in CH₂ Cl₂ (5 ml), and stirred at0 ° C. under an atmosphere of nitrogen. EDCI (0.0455 g, 0.24 mmol, 1.2equiv.), was added to the reaction mixture, and allowed to warm slowlyto room temperature whilst stirring overnight. The reaction mixture waswashed with water (30 ml), and the product extracted into CH₂ Cl₂. Theorganic layer was collected, dried with anh. MgSO₄, and the solventremoved under reduced pressure. The crude product was absorbed ontosilica gel and purified by silica gel flash column chromatography, 1-3%methanol/CH₂ Cl₂ were used as eluents. The product dried under highvacuum and was isolated as colourless oil (0.048 g, 33%); ν_(max) 3053,2983, 1729, 1601, 1243, and 1025; δ_(H) (CDCl₃) 0.84 (3H, s, 18'--CH₃),1.25-1.93 (11H, m), 1.35 (12H, t, J=7.2, P--OCH₂ CH₃), 1.12-2.74 (7H,m), 2.87-2.92 (2H, m), 4.12-4.28 (8H, m, P--OCH₂ CH₃), 4.70 (1H, dd,J=8.8, 7.1, 17'H), 6.92-7.00 (2H, m), 7.33 (1H, d, J=8.2, 1'H),7.46-7.67 (3H, m), and 8.20 (2H, dt, J=8.3, 1.6, ortho H's on Ph); δ_(C)(CDCl₃) 12.06 (1C, 18'--CH₃), 16.32 (2C, P--OCH₂ CH₃), 16.43 (2C,P--OCH₂ CH₃), 21.04 (1C, m, P₂ CHCH₂ CH₂ --), 23.25 (1C), 26.03 (1C),27.00 (1C), 27.59 (1C), 29.50 (1C), 35.68 (1C, t, J=132.1, P₂ --CHR),36.86 (1C), 38.18 (1C), 38.35 (1C), 42. 87 (1C), 43.98 (1C), 49.80 (1C),62.61 (4C, t, J=6.7, P--OCH₂ CH₃), 82.74 (1C, 17° C), 118.67 (1C),121.58 (1C), 126.43 (1C), 128.49 (2C), 129.70 (1C), 130.10 (2C), 133.45(1C), 137.84 (1C), 138.19 (1C), 148.68 (1C), and 172.72 (2C); δ_(P)(CDCl₃) 23.2; m/z (+ve ion FAB) 721 (M⁺ +H, for product containing 2D),720 (M⁺ +H, for product containing 1D), and 719 (M⁺ +H). The benzyl andethyl groups can be removed by the methods of Examples 4 and 5.

EXAMPLE 10 Synthesis of Ethyl 17-oxoestra-1,3,5, -trien-3-yl proprionate(25) ##STR20## Oestrone (0.54 g, 2.0 mmol, 1.0 equiv.), triethylamine(0.56 ml, 0.405 g, 4.0 mmol, 2.0 equiv.), were dissolved intetrahydrofuran (15 ml) and stirred at 0 ° C. under an atmosphere ofnitrogen. Ethyl malonyl chloride (0.76 ml, 0.903 g, 6.0 mmol, 3.0equiv.) was added slowly to the reaction mixture, which was allowed towarm to room temperature and stirred overnight. The reaction mixture waswashed with water (2×50 ml), and the product extracted into CH₂ Cl₂, anddried with anh. MgSO₄. The solvent was removed under reduced pressure,the crude product absorbed onto silica gel and purified by silica gelflash column chromatography, eluted with 0.5% methanol/CH₂ Cl₂. Theproduct was isolated as a colourless oil (0.144 g,19% yield); δ_(H)(CDCl₃) 0.90 (3H, s, 18'--CH₃), 1.32 (3H, t, J=7.1, --OCH₂ CH₃),1.36-1.75 (6H, m), 1.88-2.59 (7H, m), 2.91 (2H, dd, J=8.3, 3.8), 3.59(2H, s, malonate H), 4.26 (2H, q, 7.1, --OCH₂ CH₃), 6.86-6.91 (2H, m),and 7.29 (1H, d, J=8.2, 1'H); δ_(C) (CDCl₃) 13.65, 13.95, 21.41, 25.60,26.13, 29.21, 31.39, 35.68, 37.83, 41.47, 43.98, 47.75, 50.26, 61.58,118.35, 121.18, 126.30, 137.65, 138.00, 148.22 (3'C), 165.25 (--CO₂ Et),166.09 (--CO₂ Ph), and 214.04 (17'C); m/z (+ve ion FAB) 385 (38) (M⁺+H), 115 (100). EXAMPLE 11 Synthesis of Tetraethyl[4-ethoxy-4-oxo-3-(17-oxoestra-1,3,5-trienyloxycarbonyl)-butylidene]bis[phosphonate] (26) ##STR21## 25 (0.112 g, 0.291 mmol, 1.0 equiv.),and 16 (0.087 g, 0.291 mmol, 1.0 equiv.), were dissolved intetrahydrofuran and stirred at room temperature under an atmosphere ofnitrogen. A solution of lithium bis(trimethylsilyl)amide (1M) intetrahydrofuran (0.03 ml, 0.03 mmol, 0.1 equiv.) was added to thereaction mixture and stirred for 3 hours. The reaction mixture wasquenched with saturated aqueous ammonium chloride, and the productextracted into CH₂ Cl₂. The organic layer was collected and dried withanh. MgSO₄. The solvent was removed under reduced pressure and the crudeproduct adsorbed onto silica gel. The product was purified by silica gelflash column chromatography, 0.5-3% methanol/CH₂ Cl₂ as eluent. Theproduct was isolated and dried under high vacuum to give a colourlessoil (0.060 g, 30%); δ_(H) (CDCl₃) 0.91 (3H, s, 18'--CH₃), 1.27-1.72 (8H,m), 1.37 (12H, t, J=7.2, P--O--CH₂ CH₃), 1.90-2.95 (13H, m), 4.13-4.33(11H, m), 6.82-6.90 (2H, m), and 7.30 (1H, d, J=8.8, 1'H); δ_(C) (CDCl₃)13.76 (1C, 18'C), 14.06 (1C, --CO₂ CH₂ CH₃), 16.24 (2C, --PO₂ CH₂ CH₃),16.35 (2C, --PO₂ CH₂ CH₃), 21.53 (1C, P₂ CHCH₂ CH--), 24.96 (1C, m),25.70 (1C), 26.24 (1C), 29.32 (1C), 31.50 (1C), 34.28 (1C, t, J=132.1,P--C--P), 35.76 (1C), 37.97 (1C), 44.11 (1C), 17.86 (1C), 49.93-50.23(1C, m, --C(O)CHRC(O)--), 50.42 (1C), 61.77 (1C, --CO₂ CH₂ CH₃),62.66-62.98 (4C, m, P--O--CH₂ CH₃), 118.35 (1C), 121.18 (1C), 126.36(1C), 137.70 (1C), 138.08 (1C), 148.38 (1C), 167.73 (1C),168.54 (1C),and 214.15; δ_(P) (CDCl₃) 22.34, and 22.44; m/z (+ve ion FAB) 685 (57)(M⁺ +H), 239 (100); HRMS (Found: 685.29124 C₃₃ H₅₀ O₁₁ P₂ requires:685.29066).

(26) may be converted to the corresponding bisphosphonic acid by themethod of Example 5.

EXAMPLE 12 Synthesis of Tetraethyl{3,3-bis[androst-4-en-3-one-175-yloxycarbonyl]propylidene}bis[phosphonate] (27) ##STR22## Testosterone (0.500 g, 1.73 mmol, 2.2equiv.), 17 (0.363 g, 0.788 mmol, 1.0 equiv.), and4-(N,N-dimethylamino)pyridine, were dissolved in toluene (7 ml) andheated under reflux, under an atmosphere of nitrogen. After 10 daysreflux, more testosterone (0.250 g, 0.86 mmol, 1.1 equiv.) was added tothe reaction mixture, and heated under reflux conditions for another 6days. The reaction was stopped and washed with saturated aqueousammonium chloride. The product was extracted into CH₂ Cl₂ and dried withanh. MgSO₄. The solvent was removed under reduced pressure, and thecrude product absorbed onto silica gel. The product was purified bysilica gel flash column chromatography, 3% methanol/CH₂ Cl₂ was used asthe eluent. The product was isolated as a foam under a high vacuum (0.61g, 82% based on 3); δ_(H) (CDCl₃), 0.76 (3H, s, 18'--CH₃), 0.78 (3H, s,18'--CH₃), 0.80-1.80 (20H, m), 1.12 (6H, s, 19'--CH₃), 1.28 (12H, t,J=7.2), 1.94 -1.98 (2H, m), 2.05 -2.57 (13H, m), 3.94 (1H, t, J=7.6,malonate H), 4.58 (2H, q, J=8, 17'H), and 5.66 (2H, s, 4'H); δ_(C)(CDCl₃), 11.91 (1C), 12.02 (1C), 16.31 (2C), 16.42 (2C), 17.39 (2C),20.49 (2C), 23.45 (2C), 24.82-25.02 (1C, m), 27.31 (2C), 31.43 (2C),32.67 (2C), 33.88 (2C), 34.34 (1C, t, J=133.4), 35.34 (2C), 35.69 (2C),36.53 (2C), 38.57 (2C), 42.56-42.72 (2C, m), 50.17 (2C), 53.61 (2C),61.51 (1C), 62.61-62.92 (4C, m), 83.50 (1C), 83.64 (1C), 123.97 (2C),168.80 (1C), 168.88 (1C), 170.77 (2C), and 199.37 (2C); δ_(P) (CDCl₃),22.98; m/z (+ve ion FAB3) (M⁺ +H) 946 (14), 703 (87), and 461 (100).

(27) may be convert=-d to the corresponding bisphosphonic acid by themethod Example 5.

What is claimed is:
 1. Bisphosphonate derivatives of hydroxy steroidswhich are bone resorption inhibitors or bone formation stimulators, thederivatives having at least one group A in place of a hydroxy group onthe steroid molecule, where A is a group of the formula ##STR23## whereX is: (i) St--O--CO-- where St is the residue of the hydroxy steroidgiven by removal of an OH group; or(ii) R¹ --O--CO-- where R¹ is analkyl, alkenyl, cycloalkyl, aralkyl or aryl group, any of which mayoptionally be substituted;and the salts and solvates of these compounds.2. Compounds according to claim 1 wherein the steroid is an oestrogen,androgen, anabolic steroid, glucocorticoid or progestagen.
 3. Compoundsaccording to claim 1 wherein the steroid is 17 β-oestradiol, oestrone,testosterone, norethindrone, androsterone, norethandrolone ornandrolone.
 4. A compound according to claim 1, said compound being:##STR24##
 5. A pharmaceutical composition containing one or morecompounds according to claim 1 and one or more pharmaceuticallyacceptable carriers, excipients or diluents.
 6. Bisphosphonatederivatives of hydroxy steroids which are bone resorption inhibitors orbone formation stimulators, having a formula

    (St--O--CO).sub.2 CHCH.sub.2 CH(PO(OH).sub.2).sub.2

where St is the residue of the hydroxy steroid given by removal of an OHgroup.
 7. A pharmaceutical composition containing one or more compoundsaccording to claim 6 and one or more pharmaceutically acceptablecarriers, excipients or diluents.
 8. A process for the preparation of acompound according to claim 1 which comprises:(A) in the preparation ofa compound in which X is a group (i), transesterifying the carboxylicester groups of a compound of formula (7) ##STR25## (where R² and R³ areC₁₋₆ alkyl groups and may be the same or different) with the hydroxysteroid (StOH), to give a phosphonate ester (8) of the formula(St--O--CO)₂ CHCH₂ CH(PO(OR₃)₂)₂, followed by removal of the phosphonateester groups by hydrolysis; orin the preparation of a compound in whichX is a group (ii), reacting a malonate (13) of the hydroxy steroid

    R.sup.1 CO.CH.sub.2.CO.OSt                                 (13)

(where R¹ is as defined in claim 1) with a methylidene compound (10)##STR26## to give the addition product (14) ##STR27## followed byremoval of the phosphonate ester groups by hydrolysis.